Up to now two basically different methods of quenching incandescent coke have been used, i.e. the so-called wet quenching and the so-called dry quenching methods.
In the dry quenching method, of which several different alternatives were disclosed in Gluckauf 114 (1978), on pages 611/619, the sensible heat of the coke is abstracted either by direct or indirect heat exchange and mostly recovered. The coke is discharged from the plant at temperatures comprised between 150.degree. C. and 250.degree. C.
The direct heat exchange is provided by circulated gas whose heat energy is recovered by the heat exchange cycle.
An exclusively indirect cooling requires long residence times so that to ensure sufficient cooling capacity large heat exchange volumes are necessary.
Capital and operational costs of coke dry quenching plants are comparatively high.
While sizeable gaseous emissions do not develop with these systems, they involve serious practical drawbacks which require solution and relate to the development of large dust volumes during handling of the dry-quenched coke.
With wet quenching of coke according to the present state of the art the coke is cooled by evaporation of the sprayed water. Caused by thermal buoyancy, particulate emissions are produced during this treatment which may with modern quenching towers attain an order of magnitude of 50 g/t of coke. Besides there are gaseous emissions, e.g. in the form of hydrogen sulphide and carbon monoxide, as products of chemical reactions between the hot coke and water. Such reactions, if they occur at temperatures above 800.degree. C., lead to conspicuous pollutant emissions.